This invention relates generally to wheel assemblies, and especially to wheel assemblies which are employed in ground-engaging drive systems which are used in e.g. tracked vehicles and in endless belt conveyors. While the disclosure herein focuses on tracked vehicles and endless track drive systems for such vehicles, it will be understood that the invention can be employed in other endless track drive systems.
Ground-engaging endless track drive systems in tracked vehicles employ a plurality of wheel assemblies to define a track path, which path is beneficially traversed by the track in causing the vehicle to move along the ground. Such track drive systems can include, for example and without limitation, on each side of the vehicle, a drive wheel assembly disposed adjacent e.g. the rear of the vehicle, an idler wheel assembly disposed adjacent e.g. the front of the vehicle, and one or more mid-roller wheel assemblies backing up the ground-engaging surface of the track between the drive wheel assembly and the idler wheel assembly.
In some embodiments, such track systems employ, as an additional element, one or more separate and distinct tensioning wheel assemblies in e.g. an upper portion of the track path. In other embodiments, the tensioning function is integrated into the operation of one or more of the other wheel assemblies, as a secondary function in addition to the primary function of the respective wheel assembly.
The structures of the several wheel assemblies are typically designed and configured according to the specific uses for which each such wheel assembly is to be employed. Accordingly, drive wheel assemblies are structured for their driving function.
Idler wheel assemblies are structured for their function of performing a significant angle turn of the track, and typically are structured to perform or assist with functions related to steering the direction of movement of the vehicle. Since the idler wheel assembly generally does not bear the stresses of driving the vehicle, on a given vehicle, the idler wheel assemblies are typically less complex, and may be less robust, than the drive wheel assemblies.
Mid-roller wheel assemblies are structured and mounted to provide downwardly-directed support of the underlying track, and thus can be spring loaded from the frame for such support of the endless track. Mid-roller wheel assemblies generally do not perform driving or steering functions.
Similarly, tensioning wheel assemblies, not shown in the drawings, are structured for typically upwardly-directed support of the track, and thus are also typically designed to be spring loaded from the frame. As with mid-roller wheel assemblies, tensioning wheel assemblies generally do not perform driving or steering functions.
Thus, while the drive wheel assemblies and the idler wheel assemblies, which perform driving and steering functions, are typically relatively more robust, and can be more complex, mid-roller wheel assemblies and tensioning wheel assemblies typically perform less demanding functions and thus can be somewhat less robust and may be simpler in design.
Wheel assemblies used in track drive systems typically employ an outer layer of elastomeric material, such as rubber, as an outer driving surface. Such elastomeric layer is resilient, thus providing at least some cushioning of the vehicle frame from the rough terrain over which such vehicles may be operated. In addition, the rubber outer surface generates less noise against the track than does a metal outer surface of the wheel assembly. Yet further, the elastomeric, e.g. rubber, outer surface of the wheel assembly has a higher coefficient of friction than commonly available metal, whereby friction driving of the track is facilitated.
The elastomeric layer of the wheel assembly is typically mounted to a metal wheel, which is mounted to a wheel hub, the hub being mounted to a respective axle or other-mounting shaft. Various structures have been proposed for such mounting of the elastomeric layer to the wheel. There are available, for example, as conventional structures, entrapping flanges integral with the wheel wherein the flanges extend outwardly of, and partially overlie, the outer surface of the elastomeric layer, such that the flanges interfere with interface of the elastomeric surface with a track having an inner surface which is generally flat when taken across the transverse dimension of the track.
Another conventional structure includes a coiled metal spring as an outer track-engaging surface of the wheel assembly, held in place by a separate side flange which extends upwardly above the track-engaging outer surface of the wheel assembly.
Yet another conventional structure teaches spacer sleeves extending through, and apparently molded into, the elastomeric tire material and receiving bolts which extend between retaining rings on opposing sides of the tire, and wheel, through the spacer sleeves, thereby to hold the tire to the wheel.
All the above structures are quite complex, including associated cost, both of manufacturing such structures and of maintaining such structures.
In a known simpler design, for mid-roller wheel assemblies, a non-pneumatic rubber tire is adhesively mounted to an outer surface of a wheel, thereby to provide a relatively low cost wheel assembly. The wheel has an outer surface which receives the inner surface of the tire. Such adhesively-mounted tire can separate from the wheel under the severe operating conditions in which such vehicles are commonly used; and such separation requires replacement of both the tire and the hub.
It is an object of this invention to provide a relatively less complex wheel assembly wherein a relatively less complex elastomeric tire is mounted to a generally less complex wheel.
It is another object to provide such wheel assembly wherein the tire can be replaced without replacing the wheel.
It is still another object to provide such wheel assembly wherein the tire is held on the wheel by a side flange mounted to the wheel, and wherein no portion of the mounting structure passes through the tire so as to require an aperture extending transversely through the tire, outside the inner surface of the tire.
Still another object is to provide such wheel assembly wherein tire defines the entirety of the width of the outer surface of the wheel assembly.